Room Size Calculator
Calculate your room area in square feet and square meters. Select room shape, enter dimensions, and get the area instantly — plus perimeter for baseboard estimates.
ft
ft
Enter your values above to see the results.
Tips & Notes
- ✓Measure at floor level from inside wall to inside wall — this gives actual usable floor area. Walls are typically 4-6 inches thick, so inside dimensions are smaller than outside dimensions.
- ✓For L-shaped rooms, break the space into two rectangles at the natural division point, measure each rectangle separately, and add the areas together.
- ✓Convert feet and inches to decimal feet before entering: 12 ft 6 in = 12.5 ft; 15 ft 9 in = 15.75 ft; 10 ft 3 in = 10.25 ft.
- ✓Add 10% to your room area when ordering flooring or carpet to account for cuts and waste. Add 15% for diagonal tile patterns.
- ✓Use the perimeter result to estimate baseboard, crown molding, or wall trim needs — subtract door openings (each typically 3 ft wide).
Common Mistakes
- ✗Measuring from outside wall to outside wall — always measure the inside dimensions for accurate floor area. Wall thickness reduces usable space by 8-12 inches per wall pair.
- ✗Mixing feet and inches without converting — enter 14 ft 6 in as 14.5 ft, not 14.6. Each inch is 0.0833 ft, not 0.1 ft.
- ✗Forgetting to add a waste factor when ordering flooring — the calculated area is the minimum; always order 10-15% more than the exact square footage.
- ✗Measuring only the main room area without including closets and alcoves when calculating flooring needs — include all areas that will be covered.
- ✗Using room dimensions for paint calculation — wall area is different from floor area. Calculate each wall (length × height) separately for paint estimates.
Room Size Calculator Overview
Room area is the foundation of every material estimate for home improvement — flooring, carpet, tile, paint, wallpaper, and HVAC sizing all begin with accurate square footage. An error of just 10% in room measurement can mean ordering a full extra box of flooring or coming up short mid-installation.
Area formulas by room shape:
Rectangle: Area (sq ft) = Length (ft) × Width (ft) | L-Shape: Area = (L1 × W1) + (L2 × W2)
EX: Rectangular room 14 ft × 16 ft → Area = 14 × 16 = 224 sq ft → Add 10% waste for flooring → Order 246 sq ft → Perimeter = 2 × (14 + 16) = 60 ft of baseboard neededUnit conversions — quick reference:
| Square Feet | Square Meters | Square Yards | Approximate Room Size |
|---|---|---|---|
| 100 sq ft | 9.29 m² | 11.11 sq yd | Small bedroom, large bathroom |
| 150 sq ft | 13.94 m² | 16.67 sq yd | Standard bedroom (10'×15') |
| 200 sq ft | 18.58 m² | 22.22 sq yd | Master bedroom (13'×16') |
| 250 sq ft | 23.23 m² | 27.78 sq yd | Large bedroom, small living room |
| 300 sq ft | 27.87 m² | 33.33 sq yd | Living room (15'×20') |
| 400 sq ft | 37.16 m² | 44.44 sq yd | Large living room, open plan area |
| Material | Pattern | Waste Add-On | Reason |
|---|---|---|---|
| Hardwood / LVP flooring | Straight lay | +10% | End cuts, starter rows |
| Carpet | Any direction | +10% | Seams, edge trimming |
| Tile | Straight lay | +10% | Cuts at walls, breakage |
| Tile | Diagonal (45°) | +15% | More cuts per row |
| Tile | Herringbone | +20% | Angled cuts throughout |
| Wallpaper (no repeat) | Plain | +10% | Trimming, seams |
| Wallpaper (large repeat) | Pattern match | +25-35% | Pattern matching loss |
Frequently Asked Questions
Measure at floor level from one inside wall to the opposite inside wall along the longest dimension — this is your length. Then measure the perpendicular inside dimension — this is your width. For L-shaped rooms, measure each rectangular section separately: identify where the room changes direction, measure that rectangle fully, then measure the second section. Add the two areas. Use a metal tape measure for accuracy; cloth tapes can stretch. Measure twice, especially for flooring purchases.
Multiply square feet by 0.0929 to get square meters. Or divide by 10.764. Examples: 150 sq ft = 150 × 0.0929 = 13.93 m²; 200 sq ft = 18.58 m²; 300 sq ft = 27.87 m². To go the other direction (m² to sq ft), multiply by 10.764. Most European building materials are sold per square meter — use this conversion when shopping for imported tile, flooring, or wallpaper.
Calculate room area in square feet, then add a waste allowance: 10% for straight-lay hardwood or LVP; 10% for carpet; 15% for diagonal tile; 15-20% for herringbone or complex patterns. Example: 180 sq ft room, straight hardwood → order 180 × 1.10 = 198 sq ft → round up to the nearest full box quantity. Flooring is typically sold in boxes covering specific square footages — check the coverage per box and round up to the next full box.
Wall area and floor area are different calculations. For paint: measure each wall separately (length × ceiling height), add all four walls, subtract for doors (approximately 20 sq ft each) and windows (approximately 15 sq ft each). Divide total wall area by the paint coverage rate from the can label (typically 350-400 sq ft per gallon). Add 10-15% for a second coat. Example: four walls totaling 480 sq ft, minus two doors (40 sq ft) = 440 sq ft net. At 350 sq ft/gallon: 440 / 350 = 1.26 gallons for one coat → 2.5 gallons for two coats.
Typical US room sizes: master bedroom 200-300 sq ft (14'×16' average); secondary bedroom 120-180 sq ft; living room 250-350 sq ft; kitchen 150-200 sq ft; dining room 150-200 sq ft; bathroom 50-100 sq ft (full bath); home office 100-150 sq ft. A 2,000 sq ft home might have: living room 280 sq ft, kitchen/dining 350 sq ft, master bedroom 250 sq ft, two secondary bedrooms at 150 sq ft each, two bathrooms at 75 sq ft each, plus hallways and closets for the remaining area.
Divide the L-shape into two rectangles at the natural corner. Option 1 (smaller rectangle method): identify the inside corner of the L and split there. Measure each rectangle fully — length and width. Add the two areas. Option 2 (bounding box minus): measure the full outer rectangle that would surround the L-shape, then subtract the missing rectangular corner. Both methods give the same answer when done correctly. Example: L-shaped room 18'×12' with a 6'×8' cutout → bounding box = 216 sq ft, minus cutout = 216 − 48 = 168 sq ft.